For quite some time tire manufacturers have tested tires for performance characteristics on devices known as tire uniformity machines. Typically a tire is mounted and rotated and through the use of stain gauges or the like, certain force variations are measured. Such forces include radial force variations, lateral force variations and tangential force variations. These variations could cause poor riding characteristics in a tire and can often be corrected by a strategic grinding of material from an appropriate location on the tire.
These tire uniformity machines do not, however, detect variations or deformities which may be visually objectionable but which do not necessarily effect the performance of the tire. Such a deformity, such as a slight lump, depression or undulation in the sidewall of a tire, while not always effecting the performance or safety of the tire, are nevertheless objectionable in that the purchaser of the tire, in viewing the same, may feel that the tire is defective.
At the present time the only manner in which these slight defects are even attempted to be detected is manually. Either the laborer carefully visually checks every tire or else the tire is mounted and slowly rotated while the laborer places his finger lightly against the sidewall in an attempt to feel the defects. Due to the reliance on human senses, either of these procedures are highly subjective since tolerance levels cannot be clearly defined and in addition are variable between laborers and even the same laborer as fatigue and boredom take their toll. At the present time there is no known way to automatically test tires to detect these slight variations accurately.